U.S. patent application number 11/293311 was filed with the patent office on 2006-06-08 for lock-up clutch mechanism.
This patent application is currently assigned to NSK-Warner K.K.. Invention is credited to Tamotsu Fujii, Kenji Maruo, Hideaki Takabayashi.
Application Number | 20060118378 11/293311 |
Document ID | / |
Family ID | 36572957 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060118378 |
Kind Code |
A1 |
Fujii; Tamotsu ; et
al. |
June 8, 2006 |
Lock-up clutch mechanism
Abstract
The present invention provides a lock-up clutch mechanism for a
torque converter, comprising a lock-up clutch to which a friction
material having a friction surface is secured and a front cover
having an engagement surface with which the friction surface is
engaged when the friction surface is urged in an axial direction
and in which the friction surface of the friction material has a
configuration including a protruded area protruding in the axial
direction.
Inventors: |
Fujii; Tamotsu;
(Fukuroi-shi, JP) ; Maruo; Kenji; (Fukuroi-shi,
JP) ; Takabayashi; Hideaki; (Fukuroi-shi,
JP) |
Correspondence
Address: |
MILES & STOCKBRIDGE PC
1751 PINNACLE DRIVE
SUITE 500
MCLEAN
VA
22102-3833
US
|
Assignee: |
NSK-Warner K.K.
|
Family ID: |
36572957 |
Appl. No.: |
11/293311 |
Filed: |
December 5, 2005 |
Current U.S.
Class: |
192/3.28 |
Current CPC
Class: |
F16H 45/02 20130101;
F16H 2045/0289 20130101; F16H 2045/0294 20130101; Y10T 29/49
20150115; F16H 2045/0226 20130101 |
Class at
Publication: |
192/003.28 |
International
Class: |
F16H 45/02 20060101
F16H045/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2004 |
JP |
2004-354026 |
Claims
1. A lock-up clutch mechanism for a torque converter, comprising a
lock-up clutch to which a friction material having a friction
surface is secured and a front cover having an engagement surface
with which said friction surface is engaged when said friction
surface is urged in an axial direction, wherein: said friction
surface of said friction material has a configuration including a
protruded area protruding in the axial direction.
2. A lock-up clutch mechanism according to claim 1, wherein said
friction material and said front cover can be contacted with each
other in a circumferential direction.
3. A lock-up clutch mechanism according to claim 1, wherein said
protruded area is provided on a radial outer diameter side of said
friction material.
4. A lock-up clutch mechanism according to claim 2, wherein said
protruded area is provided on a radial outer diameter side of said
friction material.
5. A lock-up clutch mechanism according to claim 1, wherein said
protruded area is provided at a substantially radial central
portion of said friction material.
6. A lock-up clutch mechanism according to claim 2, wherein said
protruded area is provided at a. substantially radial central
portion of said friction material.
7. A lock-up clutch mechanism according to claim 1, wherein said
friction material has a different thickness in a radial
direction.
8. A lock-up clutch mechanism according to claim 1, wherein said
friction surface of said friction material has a curved
surface.
9. A method for manufacturing a lock-up clutch mechanism for a
torque converter, said lock-up clutch mechanism comprising a
lock-up clutch to which a friction material having a friction
surface is secured and a front cover having-an engagement surface
with which said friction surface is engaged when said friction
surface is urged in an axial direction, wherein: said friction
surface of said friction material has a curved configuration
including a protruded area protruding in the axial direction and
said curved configuration is formed by a molding process when said
friction material is secured to said lock-up clutch.
10. A method for manufacturing a lock-up clutch mechanism according
to claim 9, wherein said friction material and said front cover can
be contacted with each other in a circumferential direction.
11. A method for manufacturing a lock-up clutch mechanism according
to claim 9, wherein said protruded area is provided on a radial
outer diameter side of said friction material.
12. A method for manufacturing a lock-up clutch mechanism according
to claim 9, wherein said protruded area is provided at a
substantially radial central portion of said friction material.
13. A method for manufacturing a lock-up clutch mechanism for a
torque converter, said lock-up clutch mechanism comprising a
lock-up clutch to which a friction material having a friction
surface is secured and a front cover having an engagement surface
with which said friction surface is engaged when said friction
surface is urged in an axial direction, wherein: said friction
material has a substantially uniform axial thickness and a curved
configuration including a protruded area protruding in the axial
direction; and a protruded area protruding in the axial direction
is provided at a position of said lock-up clutch to which said
friction material is secured and the curved configuration is formed
on said friction surface.
14. A method for manufacturing a lock-up clutch mechanism according
to claim 13, wherein said friction material and said front cover
can be contacted with each other in a circumferential
direction.
15. A method for manufacturing a lock-up clutch mechanism according
to claim 13, wherein said protruded area is provided on a radial
outer diameter side of said friction material.
16. A method for manufacturing a lock-up clutch mechanism according
to claim 13, wherein said protruded area is provided at a
substantially radial central portion of said friction material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a lock-up clutch mechanism
used in a torque converter of an automatic transmission for a
vehicle and more particularly, it relates to an improvement in a
frictional sliding surface of the lock-up clutch mechanism.
[0003] 2. Related Background Art
[0004] A torque converter used in an automatic transmission can
provide smooth start, acceleration and deceleration, but has worse
transmitting efficiency since it transmits a power via fluid. Thus,
there has been proposed a technique in which, if a speed of a
vehicle exceeds a predetermined value, a lock-up clutch mechanism
is operated to connect to a drive wheel directly in order to reduce
energy loss and enhance a fuel consumption rate.
[0005] Further, in recent years, in order to further enhance the
fuel consumption rate, the lock-up clutch mechanism has been
operated even at a low speed operation of the vehicle. In this
case, in order to reduce engine vibration and transmission shock,
so-called slip lock-up control-in which the lock-up control is
performed while maintaining a slip amount at a predetermined number
of revolutions is carried out.
[0006] In general, the lock-up clutch may cause self-excited
vibration called as jadder, thereby worsening the comfort of the
vehicle considerably. The jadder is greatly influenced particularly
by unbalance of surface pressure distribution in a circumferential
direction at a friction surface during the slipping. The unbalance
of the surface pressure distribution is greatly influenced by
accuracy of the friction surface, and, for example, dispersion is
generated on the friction surface in the circumferential direction
by undulation of a piston of the lock-up clutch and/or distortion
of a fitting bolt for a drive plate provided in a front cover.
[0007] In order to suppress of occurrence of such jadder, for
example, Japanese Patent Application Laid-open No. 2004-011710
proposes a technique in which a difference in density between a
radial inner side and a radial outer side of a friction material
secured to a lock-up piston by compressing the friction material or
reduction of a .mu.-V property of the friction surface is
suppressed by providing a tapered friction material.
[0008] However, since the occurrence of the jadder greatly relies
upon the unbalance of the surface pressure distribution in the
circumferential direction at the friction surface during the
slipping, the jadder is not necessarily avoided by the technique
disclosed in the above-mentioned Japanese Patent Application
Laid-open No. 2004-011710.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the present invention is to
provide a lock-up clutch mechanism which can make surface pressure
of a friction surface in a circumferential direction uniform with a
simple construction, regardless of change in an urging force of a
piston of a lock-up clutch, thereby preventing occurrence of
jadder.
[0010] To achieve the above object, the present invention provides
a lock-up clutch mechanism for a torque converter, comprising a
lock-up clutch to which a friction material having a friction
surface is secured and a front cover-having an engagement surface
with which the friction surface is engaged when the friction
surface is urged in an axial direction and in which the friction
surface of the friction material has a configuration including a
protruded area protruding in the axial direction.
[0011] To achieve the above object, the present invention provides
a method for manufacturing a lock-up clutch mechanism for a torque
converter, the lock-up clutch mechanism comprising a lock-up clutch
to which a friction material having a friction surface is secured
and a front cover having an engagement surface with which the
friction surface is engaged when the friction surface is urged in
an axial direction and in which the friction surface of the
friction material has a curved configuration including a protruded
area protruding in the axial direction and the curved configuration
is formed by a molding process when the friction material is
secured to the lock-up clutch.
[0012] To achieve the above object, the present invention further
provides a method for manufacturing a lock-up clutch mechanism for
a torque converter, the lock-up clutch mechanism comprising a
lock-up clutch to which a friction material having a friction
surface is secured and a front cover having an engagement surface
with which the friction surface is engaged when the friction
surface is urged in an axial direction and in which the friction
material has a substantially uniform axial thickness and a curved
configuration including a protruded area protruding in the axial
direction, and a protruded area protruding in the axial direction
is provided at a position of the lock-up clutch to which the
friction material is secured and the curved configuration is formed
on the friction surface.
[0013] By providing the protruded area protruding in the axial
direction on the friction surface, even when a piston of the
lock-up clutch is urging with a relatively small urging force
during lock-up slip, since contact surface pressure at an apex of
the protruded area is high and the friction material can be
contacted with the front cover substantially uniformly in a
circumferential direction due to flexibility of the friction
material, the uniformity of the friction surface pressure in the
circumferential direction is improved.
[0014] Further, even if the urging force of the piston is changed,
the uniformity of the friction surface pressure in the
circumferential direction is maintained more stably, thereby
reducing the jadder.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an axial partial sectional view of a torque
converter with a lock-up clutch mechanism to which embodiments of
the present invention can be applied;
[0016] FIG. 2 is an enlarged partial sectional view showing a
lock-up piston and a friction material, according to a first
embodiment of the present invention;
[0017] FIG. 3 is an enlarged partial sectional view showing a
lock-up piston and a friction material, according to a second
embodiment of the present invention; and
[0018] FIG. 4 is an enlarged partial sectional view showing a
lock-up piston and a friction material, according to a third
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Now, embodiments of the present invention will be fully
explained with reference to the accompanying drawings. In the
drawings, the same parts or elements are designated by the same
reference numerals. Further, it should be noted that the
embodiments which will be described later merely exemplify the
present invention and do not intend to limit the present invention
at all.
[0020] FIG. 1 is an axial partial sectional view of a torque
converter 30 with a lock-up clutch mechanism to which the
embodiments of the present invention can be applied, showing a
released condition of a lock-up clutch. The torque converter 30
comprises a front cover 2 which constitutes a part of a housing of
the torque converter 30, an impeller 9 as a donut-shaped impeller
secured to the front cover 2, a turbine 10 as a donut-shaped
impeller having blades opposed to blades of the impeller 9, and a
stator 5 rotatably disposed between the impeller 9 and the turbine
10. A torque converter body is constituted by the impeller 9,
turbine 10 and stator 5.
[0021] The impeller 9 is connected to a crankshaft of an engine
(not shown) of a vehicle and is rotated together with the front
cover 2 in synchronous with rotation of the engine. Further, the
turbine 10 is directly connected to an output shaft 11 and is
connected to wheels (not shown) via a transmission mechanism (not
shown). The stator 5 is sandwiched centrally between the impeller 9
and the turbine 10 and serves to change a flow of fluid filled
within the torque converter 30.
[0022] Between an inner surface of the front cover 2 and an outer
surface of the turbine 10, there is provided a lock-up clutch as an
annular plate having a piston function, i.e. a lock-up piston 1,
which forms a part of the lock-up clutch mechanism and which is
rotated integrally with the output shaft 11, and a friction
material 12 is fixed and secured to a surface of the lock-up piston
which is opposed to the inner surface of the front cover 2. A
friction surface 13 of the friction material 12 is opposed to the
inner surface of the front cover 2. Incidentally, for simplicity's
sake,. "lock-up piston" will be referred merely to as "piston"
hereinafter.
[0023] A damper mechanism comprising coil springs 6 and 7 is
disposed between the outer surface of the turbine 10 and the piston
1 in order to dampen shock when the piston 1 is engaged. Further, a
central space 8 is defined at a central portion of the torque
converter 30.
[0024] Next, an operation of the piston 1 will be described. If a
speed of a vehicle exceeds a predetermined value, feedback control
is initiated by a control mechanism (not shown) so that the flow of
the fluid within the torque converter 30 defined by the impeller 9
and the turbine 1,0 is automatically changed. By such change, the
piston 1 is urged against the inner surface of the front cover 2 to
firmly engage the friction material 12 of the piston 1 with the
inner surface of the front cover 2, thereby establishing a direct
connection condition of the piston 1, with the result that a
driving force of the engine is directly transmitted to the output
shaft 11. Accordingly, since drive and output sides are
mechanically locked up (directly connected) without interposition
of the fluid, fluid loss can be prevented and a fuel consumption
rate can be enhanced.
[0025] Incidentally, the torque converter 30 is connected to an oil
pressure control mechanism (not shown), and the oil pressure
control mechanism serves to change (increase or decrease) a flow
rate of oil while maintaining a substantially constant pressure
difference (pressure difference across the piston 1) between two
oil paths on both sides of the piston 1, i.e. between outer
peripheral side and an inner peripheral side of the piston, in
order to maintain a slip condition of the lock-up piston, i.e.
piston 1.
First Embodiment
[0026] FIG. 2 is an enlarged partial sectional view showing a
piston and a friction material according to a first embodiment of
the present invention. The friction material 12 has a protruded
area 14 N protruding axially from the friction surface 13. In this
embodiment, the protruded area 14 is formed as a curves surface
between a radial inner end 13a and a radial outer end 13b of the
friction surface 13, and an axial thickness of the friction
material 12 becomes maximum at an apex 15 positioned in a
substantially central position of the friction material.
[0027] The protruded area 14 is provided through a whole
circumferential periphery of the substantially annular friction
material 12. A curved surface configuration of the friction surface
13 is formed by a molding process when the friction material 12 is
secured to the piston 1. That is to say, an additional process for
forming the curved surface configuration is not required.
[0028] In order to manufacture a lock-up clutch mechanism according
to the illustrated embodiment, first of all, the piston 1 is
prepared, and then, the friction material 12 is secured to the
piston 1. Substantially simultaneously with the securing, the
friction material 12 is molded, thereby forming the friction
surface 13 including the curved surface.
Second Embodiment
[0029] FIG. 3 is an enlarged partial sectional view showing a
piston and a friction material according to a second embodiment of
the present invention. The friction material 12 has a protruded
area 16 protruding axially from the friction surface 13. Also in
this embodiment, the protruded area 16 is formed as a curves
surface between a radial inner end 13a and a radial outer end 13b
of the friction surface 13. An axial thickness of the friction
material 12 becomes greatest at an apex 17 of the protruded area
17. In the illustrated embodiment, the apex 17 is positioned nearer
the outer end 13b of the friction material than the inner end 13a,
and a region between the apex 17 and the inner end 13a is formed as
a curved surface gently inclined.
[0030] Similar to the first embodiment, the protruded area 16 is
provided through a whole circumferential periphery of the
substantially annular friction material 12. Further, a curved
surface configuration of the friction surface 13 is formed by a
molding process when the friction material 12 is secured to the
piston 1. That is to say, an additional process for forming the
curved surface configuration is not required.
[0031] In order to manufacture a lock-up clutch mechanism according
to the illustrated embodiment, first of all, the piston 1 is
prepared, and then, the friction material 12 is secured to the
piston 1. Substantially simultaneously with the securing, the
friction material 12 is molded, thereby forming the friction
surface 13 including the curved surface.
Third Embodiment
[0032] FIG. 4 is an enlarged partial sectional view showing a
piston and a friction material according to a third embodiment of
the present invention. The friction material 12 has a protruded
area 18 protruding axially from the friction surface 13. In this
embodiment, the protruded area 18 is formed as a curves surface
between a radial inner end 13a and a radial outer end 13b of the
friction surface 13, and an axial protruded amount of the friction
material becomes maximum at an apex 19 positioned in a
substantially central position of the friction material.
[0033] Similar to the first and second embodiments, the protruded
area 18 is provided through a whole circumferential periphery of
the substantially annular friction material 12. However, in the
third embodiment, different from the first and second embodiments,
as apparent from FIG. 4, the friction material 12 is curved but has
a substantially uniform thickness.
[0034] In this embodiment, a part-of the piston 1 to which the
friction material 12 is secured has an annular ridge portion 20
ridged as a curved surface. Since the friction material 12 having
the substantially uniform thickness is secured to the ridge portion
20, after the securing, a protruded portion 18 having a curved
surface complementary to the curved surface of the ridge portion 20
is formed in the friction material 12. Further, since a curved
surface of the friction surface 13 is formed at the same time when
the friction material 12 is secured to the piston 1, an additional
process for forming the curved surface configuration is not
required.
[0035] In order to manufacture a lock-up clutch mechanism according
to the illustrated embodiment, first of all, the piston 1 having
the ridge portion 20 is prepared, and then, the friction material
12 is secured to the piston 1. When the friction material 12 is
secured, the friction surface 13 including the curved surface is
formed substantially automatically. In FIG. 4, although the ridge
portion 20 is added to the piston 1, the ridge portion 20 may be
provided by press-working the piston itself.
[0036] In the embodiments as mentioned above, although the friction
material 12 has the substantially annular shape, the friction
material is not necessarily annular, and, for example, the friction
material may be formed by arranging a plurality of friction
material segments in an annular pattern. Further, although the
friction surface 13 of the friction material 12 is formed as the
curved surface, the friction surface may include a partially flat
surface. Further, the friction material 12 may have a different
thickness in a radial direction.
[0037] This application claims priority from Japanese Patent
Application-No. 2004-354026 filed on Dec. 7, 2004, which is hereby
incorporated by reference herein.
* * * * *